Vaccines have been one of the most successful public health interventions in preventing disease and death due to infectious disease. Vaccines typically contain the causative agent of a disease, its products or its substitute which acts as an antigen without causing the disease (or causing mild disease, in some cases). Some current vaccines against, e.g., microbial pathogens, consist of live attenuated or non-virulent variant strains of microorganisms, or killed or otherwise inactivated organisms. Other vaccines utilize more or less purified components of pathogen lysates such as surface carbohydrates, recombinant pathogen-derived proteins that are sometimes fused to other molecules, or replicative viruses that produce an antigen from a pathogen. Vaccines work by inducing an endogenous immune response resulting in the activation of antigen-specific naive lymphocytes that then give rise to antibody-secreting B cells or antigen-specific effector and memory T cells or both. This approach can result in long-lived protective immunity that may be boosted from time to time by renewed exposure to the same antigenic material.
Vaccines commonly contain adjuvants that help to accelerate, prolong and/or enhance antigen-specific immune responses. Some commonly used adjuvants include, but are not limited to, aluminium salts (e.g., alum, aluminium phosphate, and aluminium hydroxide), Freund's complete adjuvant, Freund's incomplete adjuvant, Ribi's adjuvant, squalene, and MF59®.
There remains a need for safe and effective vaccines and/or for improved vaccination strategies to enhance efficacy and to provide more durable protection to pathogen exposure and challenge, without any adverse side effects (e.g., an allergic reaction).